Method for creating asymmetrical wafer

ABSTRACT

The present invention consists of a method for imparting asymmetry to a truncated annular wafer by either rounding one corner of the orientation flat, or rounding one corner of a notch. This novel method of rounding corners impart a visual and/or tactile asymmetry which can be utilized by a person in order to differentiate between the two different sides of the wafer. This inventive wafer design and method for making an asymmetric wafer is especially useful in the field of semiconductor technology and may be used on sapphire crystal wafers or any other class of wafer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 13/757,284, filed on Feb. 1, 2013, titled“Asymmetrical Wafer Configurations and Method for Creating the Same” andnaming Michael W. Matthews and Sunil B. Phatak as inventors, whichissued as U.S. Pat. No. 8,623,136 on Jan. 7, 2014, which is a divisionalapplication of U.S. patent application Ser. No. 11/756,899, filed onJun. 1, 2007, titled “Asymmetrical Wafer Configurations and Method forCreating the Same” and naming Michael W. Matthews and Sunil B. Phatak asinventors, which issued as U.S. Pat. No. 8,389,099 on Mar. 5, 2013, thefull disclosures of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to the field of semiconductor and sapphirewafers which are used to create electronic and optoelectronic devices.More particularly, the present invention relates to inventive methodsfor physically designing configurations for the wafers in order tocreate visual and tactile asymmetry which identifies the orientation ofthe crystals within the wafer.

BACKGROUND OF THE INVENTION

Crystal symmetry in sapphire and many other single crystal systems inthe past could not be determined by the unaided eye. In certainsituations, crystal symmetry considerations result in anisotropicbehavior of the crystal structure necessitating specific crystallineorientations be maintained in reference to the overall geometry of theend device or part. Currently, there are available a wide variety ofmethods to mark a wafer made of semiconductor, sapphire, or othermaterials. In reviewing the prior art, several different methods ofmarking wafers to determine the crystalline orientation were disclosed.These methods include: using various orientation flats and notches,marking the surface of the wafer with an identifying mark using a laserbeam, marking a beveled edge portion with a bar code, adding a beveledportion which aids differentiating between the top and bottom, removingthe corner of a rectangular wafer, and utilizing systems having a notchand a hole to align a wafer.

A number of methods discuss altering the wafers with various types ofmarks. The Guldi U.S. Pat. App. Pub. No. 2002/0153620 discloses a systemof marking either the surface or bevel edge of a semiconductor with alaser to form a marking such as a two -dimensional bar code along thewafer edge at specified angular positions. The Choi U.S. Pat. App. Pub.No. 2004/0124502 discloses a semiconductor wafer having a marking regionon a lower side surface of a convex edge of the wafer wherein themarking may be carved by a laser. The Yamaguchi U.S. Pat. No. 4,630,093discloses adding asymmetry to semiconductor wafers belonging to groupsIII-V having crystalline structure of the zinc blend type by providingasymmetry on the peripheral edge with regard to the middle plane. Thedisclosure further explains that when a wafer is etched, the etchingprocess is either slowed down or sped up according to whether thesurface is mesa or reverse mesa. The Arikodo U.S. Pub. No. 2004/003608discloses a semiconductor wafer having a beveled contour on its outerperiphery and an ID mark is provided on the beveled contour. TheSakaguchi U.S. Pat. Pub. No. 2001/0038153 discloses the use of a waferhaving a semiconductor layer which forms a supporting substrate and aninsulating layer therebetween whereby a mark is formed in an area otherthan upon the semiconductor layer.

The Tan U.S. Pat. Pub. No. 2001/0001077 discloses a method for producingan alignment mark on only the oxide or BPSG layer of a wafer. The AraiU.S. Pat. Pub. No. 2004/0089958 discloses a semiconductor wafer havingan ID mark formed consisting of a bar code or the like which ispositioned on the interior of a base plate. The Guldi U.S. Pat. Pub. No.2002/0153620 discloses a marking for semiconductor wafers which includesinformation such as a 2D bar code that is marked with a laser on severallocations on the wafer so that these edge markings may be used forvisual orientation.

The Shikatani U.S. Pat. No. 4,632,884 discloses a rectangularsemiconductor wafer having either a comer cut off or a V-shaped groovelocated along its edge to identify the front and back sides of thewafer. The Nakayama U.S. Pat. No. 6,909,165 B2 discloses a rectangularnitride semiconductor wafer which has a longer slanting edge and ashorter slanting edge at neighboring corners. The Yasue U.S. Pat. No.5,060,043 discloses a semiconductor wafer having angular perimeternotching to disclose crystal orientation. The notches are small so thatthey may be formed on the bar member prior to slicing. The Yasue U.S.Pat. No. 5,147,824 discloses a method of manufacturing a wafer havingangular notches to disclose crystal orientation.

The Kimura U.S. Pat. No. 5,876,819 discloses the use of a semicircularcontour which is utilized as a mark for detecting orientation of thewafer in lieu of a traditional semicircular cut out. This decreases bothstrength and uniformity of thickness in the area of the cutout. The LeeU.S. Pat. No. 5,800,906 discloses a wafer label which includes concavemarks formed on the edge of a flat zone of the wafer via use ofphotolithography or laser etching in a conventional manner. TheMiyashito U.S. Pat. No. 5,439,723 discloses a semiconductor wafer whichuses an angular notch and an aperture to achieve precision alignmentalong an orientation flat.

The Jang U.S. Pat. No. 5,956,596 discloses a round semiconductor waferhaving a flat zone and a rectangular bar code region for marking wafers.The Oishi U.S. Pat. No. 5,993,292 discloses a method of producing awafer without a notch that has a mark oriented to a notch providedearlier during processing. Similarly, the Oishi U.S. Pat. No. 6,004,405discloses a wafer having laser marks carved as a bar code upon achamfered edge. The Jantke U.S. Pat. No. 6,177,285 B1 discloses a methodfor determining crystal orientation by finding the distance betweenadjacent mask openings having a double T-shape. This method allowsorientation to be determined even by the naked eye.

The Chen U.S. Pat. No. 6,235,637 B1 discloses a method of marking asemiconductor layer using laser scribing which will not induce flat edgeparticle yield reduction or edge defects. The Ipposhi U.S. Pat. No.6,864,534 B1 discloses two types of semiconductor wafers having a notchor an orientation flat. The Arai U.S. Pat No. 7,183,178 discloses awafer support surface having a crystal orientation angular notchprovided along its outer periphery wherein the orientation of a wafermay be determined even when its outer edge has been chipped. The ArikadoU.S. Pat. No. 7,057,259 B2 discloses a semiconductor wafer having abevel contour and an ID mark formed on the bevel contour. (See theArikado disclosure, infra). The Hidaka U.S. Pat. No. 7,102,206 B2discloses a semiconductor wafer with a substrate and a method forproducing that semiconductor wherein the semiconductor has a notch and acurved portion wherein the difference in curvature between the twoshoulder portions on the notice is between 0.0 mm and 0.1 mm.

Still other patents disclose various systems of alignment marks used ondifferent types of wafers. The Bijnen U.S. Pat. App. Pub. No.2007/0031743 discloses a lithographic substrate having a plurality ofalignment marks which provide features spaced apart at differentdistances. The Roman U.S. Pat. No. 5,580,831 discloses a method forproducing alignment marks on opposing surfaces of a flat surface, suchas a semiconductor wafer. In this process, symmetrical cuts and groovesare disposed upon the surface of a wafer. Cuts being made on opposingsurfaces of the wafer are slightly offset to lessen the risk ofmechanical failure occurring. The Yoo U.S. Pat. Pub. No. 2001/0033033discloses an alignment mark configuration wherein the alignment mark isprotected from subsequent planarization using a plurality of rectangularrecesses. The Ouellet U.S. Pat. Pub. No. U.S. 2003/0032299 discloses amethod for aligning structures on the first and second sides of a waferusing transparent islets and alignment marks.

The Inoue reference, U.S. Pat. No. 5,182,233 discloses the use of acompound semiconductor pellet wherein the major surface of the pelletand the side surfaces thereof are both 100 planes and an off centeraperture is utilized to induce asymmetry into the configuration of thewafer. The Teramoto U.S. Pat. Pub. No. 2003/0102576 discloses analignment pattern and method of forming the pattern having a slopedsurface, an alignment hole, an insulation layer, and an oxide film forthe purpose of patterning a metal interconnection film. The Ido U.S.Pat. Pub. No. 2004/0262783 A1 discloses semiconductor devices havingalignment marks and imbedded portions on the surface of a wafer. Thewafer surface is also provided with a high reflectance portion and a lowreflectance portion, and an irregular reflection film arrangedinternally.

The Berge U.S. Pat. Pub. No. 2005/0118781 discloses a method whereby aplurality of alignment markers are anisotropically etched into thesubstrate of a wafer in order to determine the orientation of thecrystal axis. The Kobayashi U.S. Pat. Pub. No. 2005/0070068 discloses amethod of forming an alignment mark on a substrate by removing a portionof material in a grid like etching on the surface of a wafer. The LinU.S. Pat. No. 5,982,044 discloses an alignment pattern and algorithm forproducing the marks, which minimize misalignment due to asymmetricformation of a material layer. The pattern consists of a substantiallycircular grid and triangular etchings which are photomasked upon thewafer.

The So U.S. Pat. No. 6,261,918 B1 discloses a method of producingalignment marks in an integrated circuit by forming a basic alignmentmark, and then creating a second set of marks overlapping the first setof marks which are positioned perpendicular thereto to form apreservation pattern and then further etching to produce a checkerboardtype pattern. The wafer then undergoes CMP (Chemical MechanicalPlanarization) without damaging the first of marks. The Glenn U.S. Pat.No. 6,869,861 B1 discloses a vertical and horizontal scribe line thataids in backside alignment of the wafer. An aperture may be drilledthrough the wafer at the intersection of the scribe lines.

The Bijnen disclosure, U.S. Pat. Pub. No. 2007/0031743 discloses the useof a lithographic substrate to provide an alignment mark having aplurality of features spaced apart from one another by varyingdistances. The Pike U.S. Pat. No. 6,410,927 B1 discloses a semiconductorwafer analysis tool for scanning raw wafers which helps orient and alignwafers to a preexisting mark, which aids in the identification ofdefects prior to further processing of the wafer. The Witvrouw U.S. Pat.No. 6,740,542 B2 discloses a method for producing micromachined deviceswherein a crystalline wafer is processed to align it in the directionthat a cleavage is likely to occur in order to provide improvedresistance to crack propagation. An etching or grid is used in thisinstance.

Others devices found in prior art have rounded edges, but the primarypurpose of such a rounded edge is to prevent chipping rather than toimpart asymmetry to a substrate. The Maejima U.S. Pat. No. 4,783,225discloses a wafer having chamfered bent portions in the joint regionsand a semicircular notch, which bent portions prevent chipping of thewafer edge; the wafer is used for creating integrated circuits. TheMaejima U.S. Pat. No. 5,230,747 discloses a semiconductor wafer havingchamfered bent portions in joint regions and a cutaway portion, such asan orientation flat. Acute bends are formed in the joint parts betweenthe flat portion of the wafer and its contour to prevent chipping awayat the joint portion. The Ogino U.S. Pat. No. 5,110,764 discloses asubstantially rectangular semiconductor silicon wafer having a beveledportion asymmetrically formed which prevents its circumferential edgesfrom being chipped. Similarly, the Ogino U.S. Pat. No. 5,021,862discloses an asymmetrical circumferential edge beveled semiconductorwafer which prevents the wafer from being chipped. The Kimura U.S. Pat.No. 5,045,505 discloses a method of processing a semiconductor device bysimultaneously forming annular beveled portions on both the front andback of a wafer in order to prevent the edge of the wafer from chippingbecause the grinding operation is balanced, having equal pressure beingapplied to both front and back surfaces.

The Maejima U.S. Pat. No. 5,279,992 discloses a wafer having a curvednotch along its outer periphery and chamfered portions to preventchipping of the wafer edge. The Nishi U.S. Pat. No. 6,302,769 B1discloses a method of chamfering a disk -shaped wafer using a grindstoneto first make an angular notch in the edge, and then the grindstonemakes a semicircular edge chamfer both in the interior of the notch, andalso along the entire perimeter of the wafer. The Asano U.S. Pat. No.6,897,126 B2 discloses a method of manufacturing a compoundsemiconductor device which is given a slanted edge to reduce chippingwhen a wafer is diced along on angle between 30 and 60 degrees withrespect to the orientation flat.

Finally, many publications disclose several other ways to altersemiconductor wafers. For example, the Urakami U.S. Pub. No.2001/0048142 discloses a semiconductor substrate and method fordeveloping a trench in that substrate upon the surface of the wafer.Similarly, the Urakami U.S. Pat. App. Pub. No. 2003/0164534 discloses asemiconductor substrate and method for developing a trench in thatsubstrate. See the related Urakami disclosure, infra. The Fukuda U.S.Pat. App. Pub. No. 2004/0097084 discloses a method for grinding the rearsurface of a semiconductor to a flat surface and predeterminedthickness. In one embodiment, a sharp knife edge is formed.

The Tomita U.S. Pat. App. Pub. No. 2004/0246795 discloses a method ofcutting wafers using a large wafer and a small wafer moving together viameans of a pusher plate so that the larger wafer and the smaller wafermay be bonded to one another with their centerlines and orientationflats properly aligned. The Subramonian U.S. Pat. App. Pub. No.2006/0118920 discloses a method for forming vias that have at least onepair of opposing side walls using potassium hydroxide.

The Arai U.S. Pat. No. 7,183,178 B2 discloses a method of manufacturinga semiconductor wafer wherein a film is formed on the wafer to preventit from warping during the subsequent grinding steps. The Fournel U.S.Pat. Pub. No. 2003/0175531 discloses a process for controlling theformation of secondary structures on the surface of a crystallinestructure. The Arai U.S. Pat. Pub. No. 2005/0106840 discloses a methodof forming a semiconductor wafer wherein a film is applied to the backsurface to prevent it from warping. See the Arai reference 7,183,178,supra.

The Doris U.S. Pat. Pub. No. 2005/0280121 discloses a hybrid substrateand a method for fabricating such a substrate having a high-mobilitysurface for use with planar and/or multiple-gate metal oxidesemiconductor field effect transistors (MOSFETs). The van den BrekelU.S. Pat. No. 4,000,019 discloses a method of manufacturing asemiconductor device having a pattern of highly doped zones as well asproviding an epitaxial silicon layer on one side. The Nishimura U.S.Pat. No. 4,861,418 discloses a method of manufacturing a semiconductorcrystalline layer wherein a polycrystalline layer is formed, then aninsulating layer is formed, and finally an argonne laser beam scans thelayers to form a single crystalline layer on the wafer from theunderlying semiconductor crystals which are used as the seeds. TheMaruyama U.S. Pat. No. 5,751,055 discloses a semiconductor substratehaving a chamfer produced by vapor phase epitaxial growth in order tolocate an edge crown. The Bruel U.S. Reissue Pat. No. RE39,484 Ediscloses a process for the preparation of a semiconductor film.

For certain current substrate applications, the standard methods formarking substrates, and which methods are recommended by industrystandards such as SEMI, are not acceptable or desirable. A specificexample occurs when sapphire substrates are used in silicon-on-sapphireapplications. The tooling used for silicon deposition and resultantwafer handling do not typically accept the number of orientation flatsrequired to visually maintain crystal orientation. A non-standard methodmust be employed. The inventive asymmetrical wafer configurations andmethod for making same presented herein consist of rounding at least onecorner of a single orientation flat to impart visual and tactileasymmetry and accordingly they constitute a vast improvement over theprior art.

Nowhere in the prior is found a substantially annular wafer having atleast one truncated flat whereby at least one corner has been rounded inorder to facilitate differentiation between the two sides of the wafer.Also, nothing may be found in the prior art wherein a substantiallycircular wafer which has a notch having at least one rounded cornerwherein the configuration creates visual and tactile asymmetry in orderto determine the wafer's crystalline orientation. Because the presentinventive configuration of wafers is completely novel in the art, thepreferred methods employed to create such new products are likewisenovel.

SUMMARY OF THE INVENTION

The crystalline orientation indicators of the prior art are not ideal orcompatible with many of the machines and processes used in today'ssemiconductor industry. Specifically, standard indicators used insapphire substrates are not always compatible with silicon-on-sapphireapplications. The tooling used for silicon deposition and resultantwafer handling do not typically accept the number of orientation flatsrequired to visually maintain crystal orientation. The present inventionsolves and improves upon the many shortcomings of the prior art by beingmore effective as a visual and tactile indicator of the wafer'scrystalline orientation and it is more compatible with many of themachines and processes used currently in the industry.

One preferred embodiment of the present invention consists of atruncated substantially annular wafer which is provided with a roundedcorner on at least one corner of the orientation flat. This roundedcorner allows a user to easily determine the crystalline orientation ofthe wafer by creating an asymmetric visual and tactile indicator. Inanother preferred embodiment of the present invention, both corners ofthe flat are rounded, but each corner has been rounded to asubstantially different radii. The radii of the two rounded corners arepreferably of a deviation that is sufficient enough to be able to createvisual and tactile asymmetry in order to adequately indicate crystallineorientation.

According to the present invention, the wafers may consist of anysubstrate exhibiting different crystallographic orientation, finishand/or semiconducting properties. Such substrates may include, but arenot limited to: Sapphire, Silicon, Silicon Oxide, Aluminum Nitride,Germanium, Silicon Carbide, Gallium Arsenide, Gallium Phosphide, GalliumNitride, or their crystalline and amorphous analogs. Other commerciallyvaluable single crystal substrates are made from Lithium Niobate,Lithium Tantalate, or from materials chosen from any of the II-VIcompound semiconductor family.

Sapphire wafers, in particular, are used to produce LED's, or lightemitting diodes, laser diodes, high power and high frequency electronicdevices and integrated circuits, photovoltaic devices, as well assensors. A common practice utilized to indicate crystalline orientationin the industry is the use of secondary flats on one side of the wafersor the polishing of one side of the wafer. These common practices fordetermining sapphire flat orientation have not been ideal due to thespecific nature of sapphire and its machinery and tooling. Secondaryflats also may significantly reduce the amount of usable surface areaand thus waste expensive sapphire material. The present invention solvesthis problem by necessitating the use of only one orientation flat,while at the same time allowing the user to identify the crystallineorientation by visual or tactile asymmetry by providing at least onerounded corner on the flat.

In another preferred embodiment of the present invention, the wafer'scrystalline orientation may be indicated by providing a small notchinstead of a flat for wafers having larger diameters. Typically, forwafers of diameters of 200 mm or larger, a flat may not be used becausesuch flats would not be compatible with many of the machines and toolscurrently used on such larger wafers. Also, such flats greatly reducethe amount of usable surface area, hence wasting significant substratematerial. Thus, a small notch would be preferable or wafers of suchlarge size. Similar to the orientation flat configuration describedabove, the small notch would indicate crystalline orientation byrounding the two corners of the notch with differential radii or byrounding at least one corner to impart visual and or tactile asymmetry.These orientation notches may consist of many types of geometricconfigurations. Such geometric configurations may consist of, but arenot limited to: angular, square, trapezoidal, pie shaped,semi-spherical, elliptical, parabolic, circular or oval.

Additionally, to impart further information, such as whether thecrystalline wafer is p-type or n-type, the present inventive waferdesign may be provided with a secondary flat or notch on the wafer, witheach flat or notch having either two rounded corners each, or onerounded corner, or rounded corners of a different radii in order torepresent additional information other than crystalline orientation.

The present invention also includes a method of creating an annularwafer having at least one rounded corner on an orientation flat. Toproduce the wafers, initially single crystal ingots are grown byutilizing commercial processes. Next, the grown crystal ingots undergox-ray measurements to determine their crystalline orientation, afterwhich one side of the crystal ingots are ground down to create theorientation flat or notch before they are sliced into wafer blanks.Finally, wafers' surfaces and edges are ground, polished, cleaned, andsent on to final metrology. During this process, the corners of theorientation flat are made asymmetric either by being rounded when theflat is created, or when grinding occurs during one of the final phases.When the corners of the orientation flat are rounded, they arepreferably rounded via a standard method so that crystals with the sameorientation always contain the rounded corner on the same side. Toimplement the process, commercially available surface and edge grindingtools common in the machining and semiconductor industries would beutilized.

The present invention also includes a method of creating a substantiallycircular wafer having at least one rounded corner on an orientationnotch. The wafers are produced in the same manner as a wafer containingan orientation flat, but instead of grinding an orientation flat intothe crystal ingots, an orientation notch would be ground therein. Duringthis process, the corners of the orientation notch are made visuallyasymmetric by being rounded at either an intermediate step when thenotch is created, or during a final grinding phase. When the corners ofthe orientation notch are rounded, they preferably are rounded in astandard way so that crystal of the same orientation always have therounded corner on the same side. Again, in order to implement theprocess, commercially available surface and edge grinding tools commonin the machining and semiconductor industries would be utilized.

OBJECTS OF THE INVENTION

Thus, it is one primary object of the present invention to provide asubstantially annular wafer whereby one may readily differentiate itsopposing sides of the wafer by identifying at least one rounded corneron one side of an orientation flat, either visually or tactilely.

It is yet another primary object of the present invention to provide asubstantially annular wafer whereby one may readily differentiate itsopposing sides by rounding at least one single corner of an orientationnotch.

Another primary object of the present invention to provide a method ofmaking wafers which contain at least one rounded corner on anorientation flat from a single crystal ingot.

It is yet another primary object of the present invention to provide amethod of making wafers which contain a rounded corner of a notch from asingle crystal ingot.

It is yet another primary object of the present invention to provide animproved method for readily identifying the orientation of semiconductorwafers, sapphire wafers, or any other type of wafer or disc that has anunderlying molecular, crystalline or other structural asymmetry which isnot readily apparent from visual inspection.

Another primary object of the present invention is to providesubstantially circular wafers having a notch of substantially angularconfiguration with at least one rounded corner in order to indicatecrystalline orientation by visual or tactile asymmetry.

It is a further primary object of the present invention to provide anannular wafer having a flat with two rounded corners, whereby eachrounded corner has substantially differing radii such that it ispossible to create visual and tactile asymmetry for readily indicatingcrystalline orientation.

It is yet another primary object of the present invention to provide asubstantially circular wafer having a notch with two rounded corners,wherein each corner has been rounded with sufficiently differing radiiin order to impart visual and tactile asymmetry for the purpose ofdetermining crystalline orientation.

Another primary object of the present invention is to provide a methodof making wafers having two rounded corners on an orientation flat froma cylindrical ingot wherein each corner has been rounded withsufficiently differing radii such that they impart visual and tactileasymmetry for the purpose of indicating crystalline orientation.

It is yet another primary object of the present invention to provide amethod of making wafers having two rounded corners created on a notchfrom a cylindrical ingot, wherein each rounded corner has substantiallydifferentiating radii such that visual and tactile asymmetry may becreated in order to indicate crystalline orientation.

These and other objects and advantages of the present invention can bereadily derived from the following detailed description of the drawingstaken in conjunction with the accompanying drawings present herein andshould be considered as within the overall scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side perspective view of a wafer expanded to show the frontand backside of the wafer.

FIG. 2 is an elevated top view of the wafer with a close up insert viewof the asymmetric corners.

FIG. 3 is an ingot in side perspective view undergoing x-ray analysis todetermine orientation.

FIG. 4 is a side perspective view of an ingot which has had anorientation flat ground into it.

FIG. 5 is a side perspective view of an ingot with a flat where onecorner of the flat has been ground down.

FIG. 6 is a side perspective view of the ingot cut into slices.

FIG. 7 is a top elevation view of a wafer with a notch.

FIG. 8 is a top elevation view of the wafer with expanded insert viewsof an asymmetrical notch.

FIG. 9 is a flow chart of the process of producing a wafer with a flatwith at least one rounded corner.

FIG. 10 is a flow chart of the process of producing a wafer with a flatwith both corners rounded with differing radii.

FIG. 11 is a flow chart of the process of producing a wafer with anorientation notch with at least one rounded corner.

FIG. 12 is a flow chart of the process of producing a wafer with anorientation notch with both corners rounded with differing radii.

DETAILED DESCRIPTION OF THE DRAWINGS

One preferred embodiment of the present invention shown in FIG. 1 issubstantially annular wafer 10 which has been provided with orientationflat 40. The annular wafer 10 is preferably made from substrates of thesemiconductor compound groups that exhibit different crystallographic orfinishing properties. Such substrates may include, but are not limitedto: Sapphire, Silicon, Silicon Oxide, Aluminum Nitride, Germanium,Silicon Carbide, Gallium Arsenide, Gallium Phosphide, Gallium Nitride,or their crystalline and amorphous analogs. Substrates having othercommercially valuable single crystal substrates are made from: LithiumNiobate, Lithium Tantalate, or from the any of the II-VI compoundsemiconductor family.

Preferably, annular wafer 10 and orientation flat 40, would be utilizedin conjunction with smaller wafers having a diameter of four inches orless. On wafers of larger sizes, from 200 mm and larger diameters, anorientation flat would not generally be utilized inasmuch as it maygreatly reduce the amount of usable surface area, hence unnecessarilywasting valuable substrate material. The annular wafer 10 would be cutto a standard thickness commonly utilized within the semiconductorindustry.

Annular wafer 10, in FIG. 1, contains one orientation flat 40. FIG. 1also shows an expanded view of the backside 20 and frontside 30 ofannular wafer 10. On the backside 20 the A-axis is shown running fromthe top right to the bottom left, and the C -axis projection isperpendicular to this axis. Orientation flat 40 is shown at the bottomof the backside 20. On the frontside 30, the A-axis is shown runningfrom the top left to the bottom right, and the C-axis is perpendicularto it. Orientation flat 40 is shown on the bottom. This figureillustrates that backside 20 and frontside 30, while different, appearidentical from visual examination.

FIG. 2 shows frontside 30 of annular wafer 10 which has been providedwith orientation flat 40. Orientation flat 40 contains two corners:sharp corner 50 and rounded corner 60. These different cornerconfigurations which are provided orientation flat 40 impart visual andtactile asymmetry to the wafer 10. From this inherent symmetry, a user,by either feeling for the rounded corner 60 which differs from the feelof sharp corner 50 or by visually identifying the features, may therebydetermine at least one aspect of the molecular structure of the wafer.

Annular wafer 10 would be typically produced by common techniques wellknown in the semiconductor industry. FIG. 3 shows an initial stepwherein single crystal ingot 70 is grown according to common industrymethods. The single crystal ingot 70 is substantially cylindrical andwould be grown to size of preferably eight to twelve inches length.After it as been grown, the crystalline orientation is determined bystandard industry methods such as X-ray analysis. After the crystalorientation of the ingot 70 has been determined, it will then typicallyenter into the shaping phase.

During the shaping phase, an orientation plane 90 is ground upon thecylindrical crystal ingot 70. FIG. 4, illustrates the crystal ingot 70having an orientation plane 90. After orientation plane 90 had beenground into the crystal ingot 70, preferably at least one corner of thecrystal ingot 70 then would be rounded. FIG. 5 shows the crystal ingot70 having orientation plane 90 that has been provided with at least onerounded corner 100.

After the crystal ingot 70 had been shaped with an orientation plane 90and at least one rounded corner, the crystal ingot 70 is sliced intowafers 10. FIG. 6 shows the crystal ingot 70 having orientation plane 90and rounded corner 100 sliced into wafers 10, each of which have anorientation flat 40 and a rounded corner 60 to identify the orientationof the wafer 10. The wafers 10 are preferably sliced to a standardindustry thicknesses by machinery used in the semiconductor industry.

FIG. 7 illustrates another preferred embodiment of the present inventionconsisting of a substantially circular wafer 110 having orientationtrapezoidal notch 140, orientation square notch 150, orientationtriangular notch 160, orientation elliptical notch 170, and anorientation circular notch 180. The substantial circular wafer 110 ispreferably 100 mm or larger since the orientation notches 140, 150, 160,170, and 180 are more ideal on larger wafers because they may conservelarger amounts of usable surface area. The substantially circular wafers110 are preferably produced by the same method as the annular wafers 10,but during the shaping phase, at least one of the notches 140, 150, 160,170, and 180, would be ground into the single crystal ingot instead ofthe orientation plane 90 illustrated in FIG. 4. Although a plurality ofdiffering shapes of orientation notches are shown herein: trapezoidal140, square 150, triangular 160, elliptical 170, and circular 180, oneor more of these notches may be utilized to convey orientation or otherdesired information to the user of the wafer.

FIG. 8 shows substantially circular wafer 110 having orientationtrapezoidal notch 140, whereby the notch 140 has been provided with onesharp corner 190 and one rounded corner 191, which features readilyimpart both visual and tactile asymmetry to wafer 110. From thisinherent asymmetry, a user, by either feeling for the rounded corner 191which differs from the feel of sharp corner 190 or by visuallyidentifying the features, may thereby determine at least one aspect ofthe molecular structure of the wafer.

FIG. 9 shows a representative flow chart detailing one preferred methodof producing asymmetrical wafers in accordance with the presentinvention. An initial step is taken by providing a cylindrical crystalingot growth 210 where the crystal ingot has been grown according tocommon industry methods. After the crystal ingot has been created, itscrystalline orientation will then be determined by a common industrymethod such as an x-ray crystallography technique. After the crystallineorientation has been determined, the next step may comprise a shapingphase 220 wherein the crystal ingot may be ground to create orientationflat. One succeeding step may consist of rounding at least one corner230 of the wafer. The next step may consist of slicing 240 the crystalingot into wafers. The wafer may be further processed by grinding 250the wafer surfaces and edges. One type of final process may consistpolishing and cleaning 260 the wafers.

FIG. 10 shows a representative flow chart detailing another preferredmethod of producing an annular wafer having an orientation flat and apair of asymmetrically rounded corners. An initial step may consist ofcreating a cylindrical crystal ingot growth 310 wherein a crystal ingotis grown according to common industry methods. After the crystal ingothas been grown, its crystalline orientation may then be determined by acommon industry method such as an x-ray crystallography technique andthe like. After the crystalline orientation has been determined, asubsequent processing step may consist of a shaping phase 320 whereinthe crystal ingot may be grounded to create at least one orientationflat. A subsequent step may consist of rounding 330 both corners withsubstantially differing radii. The radii of the rounded cornerspreferably vary sufficiently from each other in order to display visualasymmetry for readily determining the wafer's interior crystallineorientation. A subsequent processing step may consist of slicing 340 thecrystal ingot into waters, after which a further processing step mayconsist of grinding 350 the wafer's surfaces and edges. A finalprocessing step may consist polishing and cleaning 360 the wafers.

FIG. 11 shows a representative flow chart detailing yet anotherpreferred embodiment of the present invention, a method for producing asubstantially circular wafer having at least one orientation notch. Aninitial step may consist of creating a cylindrical crystal ingot growth410 wherein the crystal ingot is grown according to common industrymethods. After the crystal ingot has been grown, its crystallineorientation may then be determined by a common industry method such asan x-ray crystallography technique. After the crystalline orientationhas been determined, a subsequent processing step may consist of ashaping phase 420 wherein the crystal ingot may be ground to create atleast one orientation notch. Preferably, the at least one orientationnotch may consist of many different types of geometric configurations.Such geometric configurations may include, but are not limited to:angular, trapezoidal, square, triangular, semi-spherical, elliptical,circular or oval. A subsequent step may consist of rounding at least onecorner 430 of at least one orientation notch. A further step may consistof slicing 440 the crystal ingot into wafers and then grinding 450 thewafer surfaces and edges. A final processing step may consist ofpolishing and cleaning 460 the wafers.

FIG. 12 shows a representative flow chart detailing yet anotherpreferred method of the present inventive method for producing asubstantially circular wafer having at least one orientation notch andtwo rounded corners. An initial step may consist of creating acylindrical crystal ingot growth 510 wherein a crystal ingot is grownaccording to common industry methods. After the crystal ingot has beengrown, its crystalline orientation may be determined according to commonindustry methods such as an x-ray crystallography technique. After thecrystalline orientation has been determined, a subsequent step mayconsist of a shaping phase 520 wherein the crystal ingot is ground inorder to create at least one orientation notch. A subsequent processingstep may consist of rounding 530 both corners of the at least oneorientation notch with substantially differing radii. The radii of therounded corners preferably vary from each other sufficiently in order todisplay visual and tactile asymmetry so that the user may be able toreadily determine the interior or molecular crystalline orientation. Asubsequent step may consist of slicing 540 the crystal ingot into wafersand grinding 550 the surfaces and edges of each wafer. A finalprocessing step may consist of polishing and cleaning 560 the individualwafers.

Although in the foregoing detailed description the present invention hasbeen described by reference to various specific embodiments, it is to beunderstood that modifications and alterations in the structure andarrangement of those embodiments other than those specifically set forthherein may be achieved by those skilled in the art and that suchmodifications and alterations are to be considered as within the overallscope of this invention.

What is claimed is:
 1. A method of making a plurality of wafers,comprising the steps of: determining crystalline orientation of asubstantially cylindrical crystal ingot; shaping at least oneorientation flat upon said substantially cylindrical-crystal ingot;rounding at least one corner of said orientation flat to create a visualasymmetry to identify the determined crystalline orientation; andslicing said substantially cylindrical crystal ingot into a plurality ofwafers, each of the plurality of wafers having at least one roundedcorner.
 2. The method in claim 1, further comprising: growing thesubstantially cylindrical crystal ingot.
 3. The method in claim 2,further comprising the steps of: grinding at least one surface and edgeof each of said plurality of wafers; and polishing and cleaning saidplurality of wafers.
 4. The method of claim 1, wherein said step ofrounding at least one corner of said orientation flat further comprisesrounding two corners of said orientation flat to differing radii to bevisually asymmetric with respect to one another.
 5. The method of claim1, further comprising: grinding at least one truncated flat upon saidsubstantially cylindrical crystal ingot; and grinding a secondarytruncated flat upon said substantially cylindrical crystal ingot.
 6. Themethod of claim 5, further comprising rounding at least one corner ofthe secondary truncated flat that is visually asymmetric to an opposingcorner.
 7. A method of making at least one substantially circular wafer,comprising the steps of: determining crystalline orientation of asubstantially cylindrical crystal ingot; shaping at least one notch uponsaid substantially cylindrical crystal ingot; and rounding two cornersof said at least one notch to differing radii in order to be visuallyasymmetric to each other.
 8. The method of claim 7, further comprisingthe steps of: growing the substantially cylindrical crystal ingot; andslicing said substantially cylindrical crystal ingot into a plurality ofsubstantially circular wafers.
 9. The method in claim 8, wherein saidmethod of making a substantially circular wafer further comprises thesteps of: grinding at least one surface and edge of each of saidplurality of substantially circular wafers; and polishing and cleaningeach of said plurality of substantially circular wafers.
 10. The methodof claim 7, wherein said step of shaping at least one notch upon saidsubstantially cylindrical crystal ingot further comprises shaping asecondary notch upon said substantially cylindrical crystal ingot. 11.The method of claim 10, further comprising rounding at least one cornerof the secondary notch in order to create visual asymmetry with respectto opposing corner of the secondary notch.